U.S. patent number 10,008,893 [Application Number 14/908,196] was granted by the patent office on 2018-06-26 for permanent magnet-embedded electric motor, compressor, and refrigerating and air-conditioning device.
This patent grant is currently assigned to Mitsubishi Electric Corporation. The grantee listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Kazuhiko Baba, Masahiro Nigo, Kazuchika Tsuchida.
United States Patent |
10,008,893 |
Nigo , et al. |
June 26, 2018 |
Permanent magnet-embedded electric motor, compressor, and
refrigerating and air-conditioning device
Abstract
In an interior permanent magnet motor, each of permanent magnets
has a radially-inner magnet contour surface, a radially-outer
magnet contour surface, and a pair of side-end magnet contour
surfaces. Each of magnet insertion holes has a radially-inner
insertion hole contour surface, a radially-outer insertion hole
contour surface, and a pair of side-end insertion hole contour
surfaces. The radially-outer magnet contour surface and the
radially-outer insertion hole contour surface are each formed by a
first arc surface. The radially-inner magnet contour surface and
the radially-inner insertion hole contour surface are each formed
by a second arc surface and at least one straight surface
configured to suppress movement of the permanent magnet along the
magnet insertion hole having an arc shape.
Inventors: |
Nigo; Masahiro (Tokyo,
JP), Tsuchida; Kazuchika (Tokyo, JP), Baba;
Kazuhiko (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Tokyo |
N/A |
JP |
|
|
Assignee: |
Mitsubishi Electric Corporation
(Tokyo, JP)
|
Family
ID: |
52387585 |
Appl.
No.: |
14/908,196 |
Filed: |
August 26, 2014 |
PCT
Filed: |
August 26, 2014 |
PCT No.: |
PCT/JP2014/072233 |
371(c)(1),(2),(4) Date: |
January 28, 2016 |
PCT
Pub. No.: |
WO2015/037428 |
PCT
Pub. Date: |
March 19, 2015 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20160172912 A1 |
Jun 16, 2016 |
|
Foreign Application Priority Data
|
|
|
|
|
Sep 13, 2013 [JP] |
|
|
PCT/JP2013/074849 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B
31/026 (20130101); F04B 39/0005 (20130101); F04B
53/14 (20130101); H02K 1/276 (20130101); H02K
21/16 (20130101); F04B 35/04 (20130101); H02K
1/2766 (20130101); F04B 39/121 (20130101); H02K
2213/03 (20130101) |
Current International
Class: |
H02K
1/27 (20060101); H02K 21/16 (20060101); F04B
35/04 (20060101); F04B 39/12 (20060101); F04B
53/14 (20060101); F25B 31/02 (20060101); F04B
39/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
101714805 |
|
May 2010 |
|
CN |
|
102957241 |
|
Mar 2013 |
|
CN |
|
103023166 |
|
Apr 2013 |
|
CN |
|
1 734 637 |
|
Dec 2006 |
|
EP |
|
05-236685 |
|
Sep 1993 |
|
JP |
|
10-136592 |
|
May 1998 |
|
JP |
|
11-146584 |
|
May 1999 |
|
JP |
|
H11-285185 |
|
Oct 1999 |
|
JP |
|
2002-101585 |
|
Apr 2002 |
|
JP |
|
2003-088071 |
|
Mar 2003 |
|
JP |
|
2004-260972 |
|
Sep 2004 |
|
JP |
|
2005-229798 |
|
Aug 2005 |
|
JP |
|
2005-312102 |
|
Nov 2005 |
|
JP |
|
2006-325348 |
|
Nov 2006 |
|
JP |
|
2009-195088 |
|
Aug 2009 |
|
JP |
|
4452488 |
|
Feb 2010 |
|
JP |
|
3172376 |
|
Nov 2011 |
|
JP |
|
2013-132163 |
|
Jul 2013 |
|
JP |
|
201313216 |
|
Jul 2013 |
|
JP |
|
01-043259 |
|
Jun 2001 |
|
WO |
|
20130/61427 |
|
May 2013 |
|
WO |
|
2013/094075 |
|
Jun 2013 |
|
WO |
|
2013/114541 |
|
Aug 2013 |
|
WO |
|
Other References
International Search Report of the International Searching
Authority dated Dec. 2, 2014 for the corresponding international
application No. PCT/JP2014/072233 (and English translation). cited
by applicant .
Extended European Search Report dated Jan. 13, 2017 issued in
corresponding EP patent application No. 14844440.9. cited by
applicant .
Office Action dated May 18, 2017 issued in corresponding CN patent
application No. 201480049895.6 (and English ranslation). cited by
applicant .
Office Action dated Apr. 25, 2017 issued in corresponding EP patent
application No. 14 844 440.9. cited by applicant.
|
Primary Examiner: Nguyen; Tran
Attorney, Agent or Firm: Posz Law Group, PLC
Claims
The invention claimed is:
1. An interior permanent magnet motor, comprising: a stator; and a
rotor rotatably arranged so as to be opposed to the stator, wherein
the rotor comprises a rotor core having a plurality of magnet
insertion holes formed therein, into which corresponding permanent
magnets are respectively inserted, wherein the plurality of
permanent magnets and the plurality of magnet insertion holes are
each formed into an arc shape that is convex toward a center side
of the rotor and is concave toward an outer side of the rotor,
wherein each of the permanent magnets has a radially-inner magnet
contour surface, a radially-outer magnet contour surface, and a
pair of side-end magnet contour surfaces, wherein each of the
magnet insertion holes has a radially-inner insertion hole contour
surface, a radially-outer insertion hole contour surface, and a
pair of side-end insertion hole contour surfaces, wherein the
radially-outer magnet contour surface and the radially-outer
insertion hole contour surface are each formed by an outer arc
surface, wherein each of the radially-inner magnet contour surface
and the radially-inner insertion hole contour surface is formed by
at least one straight surface located between two inner arc
surfaces, the two inner arc surfaces and the at least one straight
surface being configured to suppress movement of the permanent
magnet along the magnet insertion hole having the arc shape,
wherein air gap portions are formed between the side-end magnet
contour surfaces and the side-end insertion hole contour surfaces
when the permanent magnets are inserted into the corresponding
magnet insertion holes, wherein a contour of ends of the magnet
inserting hole in a radial direction is not tapered, and wherein a
first arc that defines the radially-outer magnet contour surface of
the permanent magnets, the two inner arc surfaces of the
radially-inner magnet contour surface of the permanent magnets, a
second arc that defines the radially-outer insertion hole contour
surface of the magnet insertion holes, and the two inner arc
surfaces of the radially-inner insertion hole contour surface of
the magnet insertion holes all have a common radius center.
2. An interior permanent magnet motor according to claim 1,
wherein, when viewed in an extending direction of a rotation center
line of the rotor, at least a part of the at least one straight
surface of the radially-inner magnet contour surface and at least a
part of the at least one straight surface of the radially-inner
insertion hole contour surface are held in contact with each
other.
3. An interior permanent magnet motor according to claim 2,
wherein, when viewed in the extending direction of the rotation
center line of the rotor, at least a part of the radially-outer
magnet contour surface and at least a part of the radially-outer
insertion hole contour surface are held in contact with each other,
at least a part of the inner arc surface of the radially-inner
magnet contour surface and at least a part of the inner arc surface
of the radially-inner insertion hole contour surface are held in
contact with each other, and at least the part of the at least one
straight surface of the radially-inner magnet contour surface and
at least the part of the at least one straight surface of the
radially-inner insertion hole contour surface are held in contact
with each other.
4. An interior permanent magnet motor according to claim 1, wherein
the at least one straight surface is formed in a direction
orthogonal to a corresponding magnetic pole center line when viewed
in a cross-section orthogonal to a rotation center line of the
rotor.
5. An interior permanent magnet motor according to claim 4,
wherein, a thickness of the permanent magnet between the outer arc
surface and the inner arc surface is represented by T1, a thickness
of the permanent magnet on the magnetic pole center line is
represented by T2, and the thickness T1 and the thickness T2 fall
within a range of 0.85<(T2/T1)<0.95.
6. An interior permanent magnet motor according to claim 1, wherein
at least one air hole is formed in the rotor core so as to be
positioned on a radially inner side with respect to the at least
one straight surface of the each of the magnet insertion holes.
7. An interior permanent magnet motor according to claim 1, wherein
an air gap is secured between a rotor outer peripheral surface of
the rotor and a stator inner peripheral surface of the stator,
wherein, when viewed in a cross-section orthogonal to the rotation
center line of the rotor, the rotor outer peripheral surface is
formed by a plurality of first radial surfaces and a plurality of
second radial surfaces, wherein each of the first radial surfaces
is positioned in a corresponding magnetic pole center portion on
the rotor outer peripheral surface, wherein each of the second
radial surfaces is positioned in a corresponding inter-pole portion
on the rotor outer peripheral surface, and wherein the first radial
surface bulges toward a radially outer side to a higher degree than
the second radial surface so that the air gap is varied in a manner
of being increased as approaching from each of the magnetic pole
center portions to the adjacent inter-pole portions.
8. An interior permanent magnet motor according to claim 1, wherein
the permanent magnets comprise ferrite magnets.
9. A compressor, comprising, in an airtight container: a motor; and
a compression element, wherein the motor comprises the interior
permanent magnet motor of claim 1.
10. A refrigeration and air conditioning apparatus, comprising the
compressor of claim 9 as a component of a refrigeration cycle.
11. An interior permanent magnet motor according to claim 1,
wherein the outer arc surface has an outer arc radius, measured
from a point on a magnetic pole center line of the rotor outside of
the radial extent of the rotor, the plurality of inner arc surfaces
each have an inner arc radius, measured from the point on the
magnetic center line of the rotor, larger than the first arc
radius.
12. An interior permanent magnet motor according to claim 1,
wherein intersections of the at least one straight surface with the
plurality of inner arc surfaces of the radially inner magnet
contour surface, and intersections of the at least one straight
surface with the plurality of inner arc surfaces of the
radially-inner insertion hole contour surface, are configured to
suppress movement of the permanent magnet along the magnet
insertion hole.
13. An interior permanent magnet motor according to claim 1,
wherein the at least one straight surface includes at least first
and second straight surfaces, the plurality of inner arc surfaces
include at least first, second, and third arc surfaces each of the
radially-inner magnet contour surface and the radially-inner
insertion hole contour surface are formed by at least the first,
second, and third arc surfaces, and the first and second straight
surfaces, the first straight surface is located between the first
and second arc surfaces, and the second straight surface is located
between the second and third arc surfaces.
14. An interior permanent magnet motor according to claim 1,
wherein an outer surface of the rotor is made up of a plurality of
first radial surfaces and a plurality of second radial surfaces,
the first radial surfaces have a first radius, measured from a
first point on a magnetic pole center line of the rotor, smaller
than a second radius of the second radial surfaces, measured from a
second point on a magnetic pole center line of the rotor, the first
radial surfaces are formed to be opposite the radially-outer magnet
contour surface and the radially-outer insertion hole contour
surface in each of the magnet insertion holes, the second radial
surfaces are formed to be opposite the air gap portions in adjacent
magnetic insertion holes, and the second point is closer to the
center point of the rotor than the first point.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a U.S. national stage application of
PCT/JP2014/072233 filed on Aug. 26, 2014, which claims priority to
International Application No. PCT/JP2013/074849 filed on Sep. 13,
2013, the contents of which are incorporated herein by
reference.
TECHNICAL FIELD
The present invention relates to an interior permanent magnet
motor, a compressor, and a refrigeration and air conditioning
apparatus.
BACKGROUND
As a related-art interior permanent magnet motor, in Patent
Literature 1, there is disclosed a configuration in which a
plurality of arc-shaped permanent magnets are embedded in a rotor
core so as to be convex toward a center side of a rotor. The
permanent magnets are respectively inserted into magnet insertion
holes formed in the rotor core, and air gap portions are secured
respectively between both side end surfaces that are both ends of
an arc of each of the magnet insertion holes and both side end
surfaces that are both ends of the arc of each of the permanent
magnets. Further, assuming that a distance between the side end
surface of the permanent magnet and an outer peripheral surface of
the rotor core is represented by Q, and an air gap between a stator
and the rotor is represented by Lg, a relationship of
Lg<Q<3Lg is satisfied. Assuming that an opening angle of
portions each receiving the side end surface of the permanent
magnet of the magnet insertion hole is represented by Am, and an
opening angle of a tooth of the stator is represented by As, a
relationship of (1/10)As<Am<(1/4)As is satisfied. In this
manner, it is intended to prevent entry of a demagnetizing field
into the permanent magnet, to thereby enhance the demagnetization
resistance.
PATENT LITERATURE
[PTL 1] JP 11-146584 A
As described above, in the configuration in which the plurality of
arc-shaped permanent magnets are embedded in the rotor core so as
to be convex toward the center side of the rotor, a portion of the
permanent magnet, which is closest to the outer peripheral surface
of the rotor, corresponds to each of the side end surfaces of the
arc shape of the permanent magnet. When a large current flows
through the stator to apply a demagnetizing field to the rotor, the
side end surfaces of the permanent magnet are most easily
demagnetized. Therefore, the air gap portions are respectively
secured between the magnet insertion hole and the side end surfaces
of the permanent magnet, thereby suppressing the demagnetization of
the permanent magnet.
However, in the arc-shaped permanent magnet, in general, an arc
that is a contour of the permanent magnet on a radially outer side
and an arc that is a contour of the permanent magnet on a radially
inner side are concentric with each other. Thus, the permanent
magnet may be moved inside the magnet insertion hole due to an
electromagnetic force generated during the drive of the motor,
thereby causing difficulty in securing the air gap portions
configured to suppress the demagnetization in some cases.
Further, as a countermeasure therefor, the following method is
conceivable. A width of both the side end surfaces of the magnet
insertion hole is set smaller than a width of both the side end
surfaces of the permanent magnet so as to form a pair of abutment
portions in the vicinities of the side end surfaces of the magnet
insertion hole, which are configured to be held in contact with the
side end surfaces of the permanent magnet, respectively. Through
the contact between those abutment portions and both the side end
surfaces of the permanent magnet, the movement of the permanent
magnet is restricted while securing the air gap portions between
both the side end surfaces of the magnet insertion hole and both
the side end surfaces of the permanent magnet.
However, in the above-mentioned method, the width of the magnet
insertion hole is reduced so that the magnetic resistance is
reduced. Accordingly, an effect of suppressing the demagnetization,
which is attained by the air gap portions, may be reduced.
SUMMARY
The present invention has been made in view of the above, and has
an object to provide an interior permanent magnet motor capable of
restricting movement of a permanent magnet without relying on the
presence of abutment portions of a magnet insertion hole to be held
in contact with side end surfaces of the permanent magnet.
In order to achieve the object described above, according to one
embodiment of the present invention, there is provided an interior
permanent magnet motor, including: a stator; and a rotor rotatably
arranged so as to be opposed to the stator, in which the rotor
includes a rotor core having a plurality of magnet insertion holes
formed therein, into which corresponding permanent magnets are
respectively inserted, in which the plurality of permanent magnets
and the plurality of magnet insertion holes are each formed into an
arc shape that is convex toward a center side of the rotor, in
which each of the permanent magnets has a radially-inner magnet
contour surface, a radially-outer magnet contour surface, and a
pair of side-end magnet contour surfaces, in which each of the
magnet insertion holes has a radially-inner insertion hole contour
surface, a radially-outer insertion hole contour surface, and a
pair of side-end insertion hole contour surfaces, in which the
radially-outer magnet contour surface and the radially-outer
insertion hole contour surface are each formed by a first arc
surface, in which the radially-inner magnet contour surface and the
radially-inner insertion hole contour surface are each formed by a
second arc surface and at least one straight surface configured to
suppress movement of the permanent magnet along the magnet
insertion hole having the arc shape, and in which air gap portions
are formed between the side-end magnet contour surfaces and the
side-end insertion hole contour surfaces under a state in which the
permanent magnets are inserted into the corresponding magnet
insertion holes.
Further, when viewed in an extending direction of a rotation center
line CL of the rotor, at least a part of the straight surface of
the radially-inner magnet contour surface and at least a part of
the straight surface of the radially-inner insertion hole contour
surface may be held in contact with each other.
In addition, when viewed in the extending direction of the rotation
center line CL of the rotor, at least a part of the radially-outer
magnet contour surface and at least a part of the radially-outer
insertion hole contour surface may be held in contact with each
other, at least a part of the second arc surface of the
radially-inner magnet contour surface and at least a part of the
second arc surface of the radially-inner insertion hole contour
surface may be held in contact with each other, and at least the
part of the straight surface of the radially-inner magnet contour
surface and at least the part of the straight surface of the
radially-inner insertion hole contour surface may be held in
contact with each other.
The straight surface may be formed in a direction orthogonal to the
corresponding magnetic pole center line when viewed in a
cross-section orthogonal to the rotation center line of the
rotor.
Assuming that a thickness of the permanent magnet between the first
arc surface and the second arc surface is represented by T1, and a
thickness of the permanent magnet on the magnetic pole center line
is represented by T2, the thickness T1 and the thickness T2 may
fall within a range of 0.85.ltoreq.(T2/T1).ltoreq.0.95.
At least one air hole may be formed in the rotor core so as to be
positioned on a radially inner side with respect to the straight
surface of the each of the magnet insertion holes.
An air gap may be secured between a rotor outer peripheral surface
of the rotor and a stator inner peripheral surface of the stator.
When viewed in the cross-section orthogonal to the rotation center
line of the rotor, the rotor outer peripheral surface may be formed
by a plurality of first radial surfaces and a plurality of second
radial surfaces. Each of the first radial surfaces may be
positioned in a corresponding magnetic pole center portion on the
rotor outer peripheral surface. Each of the second radial surfaces
may be positioned in a corresponding inter-pole portion on the
rotor outer peripheral surface. The first radial surface may bulge
toward a radially outer side to a higher degree than the second
radial surface so that the air gap is varied in a manner of being
increased as approaching from each of the magnetic pole center
portions to the adjacent inter-pole portions.
The permanent magnets may be ferrite magnets.
Further, in order to achieve the same object, according to one
embodiment of the present invention, there is also provided a
compressor. The compressor of the one embodiment of the present
invention includes, in an airtight container: a motor; and a
compression element. The motor is the above-mentioned interior
permanent magnet motor of the one embodiment of the present
invention.
Further, in order to achieve the same object, according to one
embodiment of the present invention, there is also provided a
refrigeration and air conditioning apparatus. The refrigeration and
air conditioning apparatus of the one embodiment of the present
invention includes the above-mentioned compressor of the one
embodiment of the present invention as a component of a
refrigeration cycle.
According to the one embodiment of the present invention, the
movement of the permanent magnet may be restricted without relying
on the presence of the abutment portions of the magnet insertion
hole to be held in contact with the side end surfaces of the
permanent magnet.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a view for illustrating a cross-section orthogonal to a
rotation center line of an interior permanent magnet motor
according to a first embodiment of the present invention.
FIG. 2 is a view for illustrating a peripheral part of one
permanent magnet and a peripheral part of one tooth tip portion
corresponding to the one permanent magnet in FIG. 1 in an enlarged
manner.
FIG. 3 is a view according to the first embodiment, for
illustrating a shape of one permanent magnet.
FIG. 4 is a view for illustrating a shape of a magnet insertion
hole under a state in which the permanent magnet is not inserted in
FIG. 2.
FIG. 5 is a graph for comparing demagnetizing factors with respect
to a motor current between the first embodiment and an illustration
example.
FIG. 6 is a view according to the illustration example in the same
manner as that of FIG. 2.
FIG. 7 is a view according to a second embodiment of the present
invention in the same manner as that of FIG. 2.
FIG. 8 is a graph for showing a relationship between a thickness of
the permanent magnet and an amount of a magnetic flux that
interlinks with a stator.
FIG. 9 is a view according to a third embodiment of the present
invention in the same manner as that of FIG. 3.
FIG. 10 is a vertical sectional view of a rotary compressor having
the interior permanent magnet motor mounted therein according to a
fifth embodiment of the present invention.
DETAILED DESCRIPTION
Now, embodiments of the present invention are described referring
to the accompanying drawings. Note that, in the drawings, the same
reference symbols represent the same or corresponding parts. Note
that, FIG. 2, FIG. 4, and FIG. 7 are all partially enlarged views
extracting a part from an entire configuration in the illustration
of FIG. 1, and for the sake of clarity of illustration, the
hatching is omitted.
First Embodiment
FIG. 1 is a view for illustrating a cross-section orthogonal to a
rotation center line of an interior permanent magnet motor
according to a first embodiment of the present invention. FIG. 2 is
a view for illustrating a peripheral part of one permanent magnet
and a peripheral part of one tooth tip portion corresponding to the
one permanent magnet in an enlarged manner. FIG. 3 is a view for
illustrating a shape of one permanent magnet. FIG. 4 is a view for
illustrating a shape of a magnet insertion hole under a state in
which the permanent magnet is not inserted.
An interior permanent magnet motor 1 includes a stator 3 and a
rotor 5 rotatably arranged so as to be opposed to the stator. The
stator 3 includes a plurality of tooth portions 7. Each of the
plurality of tooth portions 7 is adjacent to other tooth portions 7
through intermediation of corresponding slot portions 9. The
plurality of tooth portions 7 and a plurality of the slot portions
9 are arranged alternately at equal intervals in a circumferential
direction. A publicly known stator winding (not shown) is wound
around each of the plurality of tooth portions 7 in a publicly
known manner.
The rotor 5 includes a rotor core 11 and a shaft 13. The shaft 13
is coupled to an axial center portion of the rotor core 11 by
shrink fitting, press fitting, or the like to transmit rotational
energy to the rotor core 11. An air gap 15 is secured between an
outer peripheral surface of the rotor 5 and an inner peripheral
surface of the stator 3.
In such a configuration, the rotor 5 is held on an inner side of
the stator 3 through intermediation of the air gap 15 so as to be
rotatable about a rotation center line CL (rotation center of the
rotor, axial line of the shaft). Specifically, a current having a
frequency synchronized with an instructed number of revolutions is
supplied to the stator 3 to generate a rotation magnetic field,
thereby rotating the rotor 5. The air gap 15 between the stator 3
and the rotor 5 is, for example, an air gap of from 0.3 mm to 1
mm.
Next, configurations of the stator 3 and the rotor 5 are described
in detail. The stator 3 includes a stator core 17. The stator core
17 is formed by, for example, punching magnetic steel plates each
having a thickness of from about 0.1 mm to about 0.7 mm into a
predetermined shape, and laminating a predetermined number of the
magnetic steel plates while fastening the magnetic steel plates by
caulking. In this case, as an example, the magnetic steel plates
each having a thickness of 0.35 mm are used.
The stator core 17 has nine slot portions 9 radially formed on a
radially inner side thereof at substantially equal intervals in the
circumferential direction. Further, a region between the adjacent
slot portions 9 in the stator core 17 is referred to as the tooth
portion 7. Each of the tooth portions 7 extends in a radial
direction, and protrudes toward the rotation center line CL.
Further, a most part of the tooth portion 7 has a substantially
constant width in the circumferential direction over a range from a
radially outer side to a radially inner side. However, a distal end
portion of the tooth portion 7, which is located on the radially
innermost side, has a tooth tip portion 7a. Each tooth tip portion
7a is formed into an umbrella shape with its both side portions
expanding in the circumferential direction.
The stator winding (not shown) forming a coil (not shown)
configured to generate a rotational magnetic field is wound around
the tooth portion. The coil is formed by directly winding a magnet
wire around the magnetic pole tooth through intermediation of an
insulator. This winding method is referred to as a concentrated
winding. The coil is connected in three-phase Y connection. The
number of turns and a wire diameter of the coil are determined
depending on required characteristics (number of revolutions,
torque, and the like), the voltage specifications, and the
sectional area of the slot. In this case, in order to facilitate
the winding, separated teeth are developed in a band shape, and,
for example, a magnet wire having a wire diameter .phi. of from
about 0.8 mm to about 1.0 mm is wound around each of the magnetic
pole teeth by about 50 turns to about 100 turns. After the winding,
the separated teeth are rounded into an annular shape and welded,
to thereby form the stator.
The rotatably held shaft 13 is arranged in the vicinity of a center
of the stator 3. Further, the rotor 5 is fitted onto the shaft 13.
The rotor 5 includes the rotor core 11, and similarly to the stator
core 17, the rotor core 11 is also formed by, for example, punching
magnetic steel plates each having a thickness of from about 0.1 mm
to about 0.7 mm into a predetermined shape, and laminating a
predetermined number of the magnetic steel plates while fastening
the magnetic steel plates by caulking. In this case, as an example,
the magnetic steel plates each having a thickness of 0.35 mm are
used. Inter-pole thin portions having a uniform thickness are each
secured between a rotor outer peripheral surface 25 and a side-end
insertion hole contour surface 57 described later. Those inter-pole
thin portions each serve as a path for a leakage magnetic flux
between the adjacent magnetic poles, and hence it is preferred that
the inter-pole thin portion have a thickness as small as possible.
In this case, as an example, the inter-pole thin portion is set to
0.35 mm, which is approximately as large as the thickness of the
magnetic steel plate, as the minimum width that allows press
work.
A plurality of permanent magnets 19 (six permanent magnets 19 in
this specific example), which are magnetized so that the N poles
and the S poles are alternately positioned, are arranged in the
rotor core 11. Referring to FIG. 1, each of the permanent magnets
19 is curved into an arc shape and arranged so that a convex
portion side of the arc shape faces the center side of the rotor 5.
In more detail, magnet insertion holes 21 as many as the number of
the plurality of permanent magnets 19 are formed in the rotor core
11. The corresponding permanent magnets 19 are inserted into a
plurality of the magnet insertion holes 21, respectively. That is,
the plurality of permanent magnets 19 and the plurality of magnet
insertion holes 21 are each formed into an arc shape that is convex
toward the center side of the rotor 5. Further, as illustrated in
FIG. 1, one permanent magnet 19 is inserted into one magnet
insertion hole 21. Note that, the number of magnetic poles of the
rotor 5 may be any number as long as the number is two or more. The
case of six poles is exemplified in this embodiment.
FIG. 2 is a view for illustrating a peripheral part of one
permanent magnet and a peripheral part of one tooth tip portion
corresponding to the one permanent magnet in FIG. 1 in an enlarged
manner. As illustrated in FIG. 2, the air gap 15 between the rotor
outer peripheral surface 25 and a stator inner peripheral surface
27 is varied in the circumferential direction. In the first
embodiment, a radius R0 of the stator inner peripheral surface 27
from the rotation center line CL is constant. Therefore, the rotor
outer peripheral surface 25 partially bulges toward the radially
outer side so that the above-mentioned variation of the air gap 15
in the circumferential direction is attained.
The rotor outer peripheral surface 25 has a plurality of first
radial surfaces 29 and a plurality of second radial surfaces 31
when viewed in the cross-section in FIG. 2 (cross-section
orthogonal to the rotation center line CL). Each of the first
radial surfaces 29 corresponds to a cross-section of a convex
surface positioned on a corresponding magnetic pole center portion
on the rotor outer peripheral surface 25. Each of the second radial
surfaces 31 corresponds to a cross-section of a cylindrical surface
positioned on a corresponding inter-pole portion on the rotor outer
peripheral surface 25. The first radial surfaces 29 bulge toward
the radially outer side to a higher degree than the second radial
surfaces 31. Each of the second radial surfaces 31 is continuous
from end portions of a corresponding pair of the first radial
surfaces 29. That is, the plurality of first radial surfaces 29 and
the plurality of second radial surfaces 31 are alternately arrayed
in the circumferential direction.
With the rotor outer peripheral surface 25 and the stator inner
peripheral surface 27, which are opposed to each other as described
above, the air gap 15 is varied over an entire circumference in a
manner of being increased as approaching from each of the magnetic
pole center portions to the adjacent inter-pole portions.
As a specific example, a minimum air gap 15 on a magnetic pole
center line ML among the air gaps 15 each between the first radial
surface 29 of the rotor outer peripheral surface 25 and the stator
inner peripheral surface 27 is 0.6 mm. Further, in the
cross-section of FIG. 2, an air gap 15 on a boundary line BL
passing through an intersection point (connection point, boundary
point) between the first radial surface 29 and the second radial
surface 31 is 0.9 mm. The air gap 15 between the first radial
surface 29 and the stator inner peripheral surface 27 becomes
smaller as approaching to the magnetic pole center ML in a range of
the first radial surface 29. On the other hand, an air gap 15
between the second radial surface 31 and the stator inner
peripheral surface 27 is uniform in a range of the second radial
surface 31. Note that, each of the first radial surfaces 29 and a
pair of the second radial surfaces 31 adjacent to both sides of the
corresponding first radial surface 29 are formed to be line
symmetric with respect to the magnetic pole center ML of the
corresponding first radial surface 29.
Note that, a center of a radius R1 of the above-mentioned first
radial surface 29 is located at a position on the magnetic pole
center ML, which is displaced toward a corresponding magnetic pole
side (radially outer side) from a rotor center (rotation center
line CL). A center of a radius R2 of the second radial surface 31
and a center of the radius R0 of the stator inner peripheral
surface 27 are located on the rotor center (rotation center line
CL).
Next, details of the permanent magnets and the magnet insertion
holes are described. FIG. 3 is a view for illustrating a shape of
one permanent magnet according to the first embodiment. FIG. 4 is a
view for illustrating a shape of the magnet insertion hole under a
state in which the permanent magnet is not inserted in FIG. 2.
The permanent magnets 19 each have a radially-inner magnet contour
surface 43, a radially-outer magnet contour surface 45, and a pair
of side-end magnet contour surfaces 47. Further, the magnet
insertion holes 21 each have a radially-inner insertion hole
contour surface 53, a radially-outer insertion hole contour surface
55, and a pair of side-end insertion hole contour surfaces 57. The
radially-outer magnet contour surface 45 and the radially-outer
insertion hole contour surface 55 are each formed by a first arc
surface having a first arc radius A1. On the other hand, the
radially-inner magnet contour surface 43 is formed by a straight
surface 49 and a second arc surface 43a having a second arc radius
A2 larger than the first arc radius A1. Similarly, the
radially-inner insertion hole contour surface 53 is formed by a
straight surface 59 and a second arc surface 53a having the second
arc radius A2.
Note that, the permanent magnet 19 is inserted into the magnet
insertion hole 21, and hence the first arc radius A1 and the second
arc radius A2 in the magnet insertion hole 21 and the first arc
radius A1 and the second arc radius A2 in the permanent magnet 19
are not equal to each other in an extremely strict sense. However,
the permanent magnet 19 is closely fitted into the magnet insertion
hole 21, and for the sake of easy understanding, common names and
reference symbols are used on the permanent magnet side and on the
magnet insertion hole side.
The first arc radius A1 and the second arc radius A2 have a common
radius center, and the common radius center is located on the
radially outer side with respect to the permanent magnet 19 and the
magnet insertion hole 21 and on the corresponding magnetic pole
center line ML. In other words, the radially-inner magnet contour
surface (radially-inner insertion hole contour surface) and the
radially-outer magnet contour surface (radially-outer insertion
hole contour surface) are formed concentrically. The center of the
first arc surface and the center of the second arc surface coincide
with an orientation center (orientation focal point) of the
permanent magnet.
When viewed in the cross-section having the rotation center line CL
of the rotor 5 as the normal as in FIG. 2 to FIG. 4, the straight
surface 49 and the straight surface 59 extend along a virtual base
plane orthogonal to the magnetic pole center line ML. That is, the
straight surface 49 and the straight surface 59 are formed in a
direction orthogonal to the corresponding magnetic pole center line
ML.
Further, in FIG. 2 and FIG. 3, the pair of side-end magnet contour
surfaces 47 each connect together corresponding end portions of the
radially-inner magnet contour surface 43 and the radially-outer
magnet contour surface 45. In FIG. 2 and FIG. 4, the pair of
side-end insertion hole contour surfaces 57 each connect together
corresponding end portions of the radially-inner insertion hole
contour surface 53 and the radially-outer insertion hole contour
surface 55.
As illustrated in FIG. 2, under a state in which the permanent
magnet 19 is inserted into the corresponding magnet insertion hole
21, air gap portions 61 are formed each between the side-end magnet
contour surface 47 and the side-end insertion hole contour surface
57. Further, the radially-outer magnet contour surface 45 and the
radially-outer insertion hole contour surface 55 are held in
contact with each other, the second arc surface 43a of the
radially-inner magnet contour surface 43 and the second arc surface
53a of the radially-inner insertion hole contour surface 53 are
held in contact with each other, and the straight surface 49 of the
radially-inner magnet contour surface 43 and the straight surface
59 of the radially-inner insertion hole contour surface 53 are held
in contact with each other. Note that, as one example, the size of
the air gap portion 61 (interval between the side-end magnet
contour surface 47 and the side-end insertion hole contour surface
57) is about 1.5 mm.
Further, when viewed in the cross-section having the rotation
center line CL of the rotor 5 as the normal, the permanent magnet
19 and the magnet insertion hole 21 are each formed to be line
symmetric with respect to the corresponding magnetic pole center
line ML. In particular, in the first embodiment, when viewed in the
cross-section having the rotation center line CL of the rotor 5 as
the normal, the straight surface 49 and the straight surface 59 are
each formed to be line symmetric with respect to the corresponding
magnetic pole center line.
Next, an action of the interior permanent magnet motor according to
the first embodiment, which is constructed as described above, is
described. In the rotor in which the arc-shaped permanent magnets
are arranged in the rotor core so that the convex portion sides
face the center side of the rotor, the surface of each magnet is
curved into an arc shape. Thus, the area of the surface of each
magnet can be increased to increase the amount of the magnetic flux
generated from the permanent magnets. Thus, the current to be
applied to the motor can be reduced, thereby being capable of
attaining the highly efficient motor. Alternatively, the volume of
the motor can be reduced. However, in the rotor having the
above-mentioned configuration, a portion of the permanent magnet,
which is closest to the rotor outer peripheral surface (having the
smallest magnetic resistance), corresponds to side surface portions
of the arc-shaped permanent magnet. When a large current flows
through the stator to apply a demagnetizing field to the rotor, the
side surface portions of the permanent magnet are most easily
demagnetized. Therefore, the side end is formed smaller in the
permanent magnet than in the magnet insertion hole so as to secure
the air gap portions each between the side-end insertion hole
contour surface of the magnet insertion hole and the side-end
magnet contour surface of the permanent magnet, thereby enabling
the permanent magnet to be hardly demagnetized. Note that,
chamfered portions 47a, which may further increase the interval
from the side-end insertion hole contour surface 57 of the magnet
insertion hole 21, are formed in the permanent magnet at portions
between the side-end magnet contour surface and the radially-inner
magnet contour surface and between the side-end magnet contour
surface and the radially-outer magnet contour surface, thereby
enabling the permanent magnet to hardly interlink with the
demagnetizing field.
Further, on the other hand, when the arc of the permanent magnet on
the inner peripheral side and the arc thereof on the outer
peripheral side are concentric with each other as described above,
the permanent magnet may be moved inside the magnet insertion hole
due to an electromagnetic force generated during the drive of the
motor, thereby causing difficulty in securing the air gap portions
configured to suppress the demagnetization. As a countermeasure
therefor, the following method is conceivable. A width of both the
side end surfaces of the magnet insertion hole is set smaller than
a width of both the side end surfaces of the permanent magnet so as
to form a pair of abutment portions in the vicinities of the side
end surfaces of the magnet insertion hole, which are configured to
be held in contact with the side end surfaces of the permanent
magnet, respectively. Through the contact between those abutment
portions and both the side end surfaces of the permanent magnet,
the movement of the permanent magnet is restricted while securing
the air gap portions between both the side end surfaces of the
magnet insertion hole and both the side end surfaces of the
permanent magnet. However, in the above-mentioned method, the width
of the magnet insertion hole is reduced so that the magnetic
resistance is reduced. Accordingly, there is a problem in that an
effect of suppressing the demagnetization, which is attained by the
air gap portions, may be reduced.
To cope with such a problem, in the first embodiment, the straight
surfaces are formed on both the radially-inner magnet contour
surface of the permanent magnet and the radially-inner insertion
hole contour surface of the magnet insertion hole. With this
configuration, even though the permanent magnet and the magnet
insertion hole are each formed into the arc shape that is convex
toward the center side of the rotor, and the air gap portions are
each secured between the side-end magnet contour surface of the
permanent magnet and the side-end insertion hole contour surface of
the magnet insertion hole, when the permanent magnet is to be moved
along the arc-shaped magnet insertion hole, the straight surface of
the permanent magnet is caught on the arc surface of the
radially-inner insertion hole contour of the magnet insertion hole,
or the arc surface of the radially-inner magnet contour of the
permanent magnet is caught on the straight surface of the magnet
insertion hole. In this manner, the movement of the permanent
magnet along the arc-shaped magnet insertion hole can be
suppressed. This suppression is attained when, for example, under
the state in which the permanent magnet is inserted into the magnet
insertion hole, as viewed in an extending direction of the rotation
center line CL of the rotor (insertion direction of the permanent
magnet), at least a part of the straight surface of the
radially-inner magnet contour surface and at least a part of the
straight surface of the radially-inner insertion hole contour
surface are held in contact with each other. Further, description
is given of an example of the illustration. Under the state in
which the permanent magnet is inserted into the magnet insertion
hole, as viewed in the extending direction of the rotation center
line CL of the rotor (insertion direction of the permanent magnet),
the radially-outer magnet contour surface and the radially-outer
insertion hole contour surface are held in contact with each other
entirely or partially, the second arc surface of the radially-inner
magnet contour surface and the second arc surface of the
radially-inner insertion hole contour surface are held in contact
with each other entirely or partially, and the straight surface of
the radially-inner magnet contour surface and the straight surface
of the radially-inner insertion hole contour surface are held in
contact with each other entirely or partially. With this, even
though the permanent magnet and the magnet insertion hole are each
formed into the arc shape that is convex toward the center side of
the rotor, and the air gap portions are each secured between the
side-end magnet contour surface of the permanent magnet and the
side-end insertion hole contour surface of the magnet insertion
hole, the movement of the permanent magnet inside the magnet
insertion hole can be suppressed. As described above, the
efficiency of the motor can be enhanced and the compactification of
the motor can be attained. Further, the movement of the permanent
magnet can be restricted while avoiding the reduction of the effect
of suppressing the demagnetization. In particular, when ferrite
magnets are used as the permanent magnets, the ferrite magnet has
coercivity lower than that of a rare-earth magnet, and hence the
effect of enabling the magnet to be hardly demagnetized is more
remarkably exerted. That is, the movement of the permanent magnet
can be restricted without relying on the presence of the abutment
portions of the magnet insertion hole to be held in contact with
the side end surfaces of the permanent magnet.
Further, the straight surfaces are formed on the portions of the
permanent magnet and the magnet insertion hole on the radially
inner side so as to extend perpendicularly to the magnetic pole
center line. Thus, the movement of the permanent magnet can be
restricted without degrading the performance and the
demagnetization characteristics, and the range of the drive current
can be increased and the output can be improved.
The ferrite magnets are used as the permanent magnets, and the
center of the first arc surface and the center of the second arc
surface are set to coincide with the orientation center of the
permanent magnet. In this case, the radially inner surface and the
radially outer surface of the ferrite magnet are formed into a
certain concentric arc shape, and the thickness of the ferrite
magnet in a radial direction of the curvature is uniformly
maintained at about 6 mm excluding the straight surface. The magnet
to which an orientation magnetic field is applied from the center
of the concentric arcs is used, and the magnet is inserted into the
magnet insertion hole having a shape conforming to the magnet. With
this, the magnetic flux of the permanent magnet is generated in a
direction perpendicular to the first arc surface and the second arc
surface, and hence the magnetic flux of the permanent magnet is
uniformly generated in a core portion corresponding to the magnetic
pole surface without causing local concentration of the magnetic
flux. Thus, the magnetic flux of the permanent magnet effectively
interlinks with the stator. Further, the shapes of the ferrite
magnets are individually molded using a die. Therefore, the ferrite
magnets have a higher degree of freedom in shape than the
rare-earth magnets obtained by slicing a molded block, and hence
are also suitable for realizing the above-mentioned specific curved
shape in which the arc surface and the straight surface are
mixed.
Note that, an example of an effect of improving a demagnetizing
factor in the interior permanent magnet motor of the first
embodiment is described. FIG. 5 is a graph for comparing
demagnetizing factors with respect to a motor current between the
first embodiment and an illustration example when the stator is
energized so that an armature magnetic flux in a phase opposite to
the permanent magnet of the rotor is generated. The solid line in
the graph indicates a result of the first embodiment, and the
dotted line in the graph indicates a result of the illustration
example. FIG. 6 is a view according to the illustration example in
the same manner as that of FIG. 2. As illustrated in FIG. 6, the
illustration example serving as an object to be compared has a
configuration that the air gap portions are secured each between
the side-end insertion hole contour surface of the magnet insertion
hole and the side-end magnet contour surface of the permanent
magnet, but the straight surfaces illustrated in the first
embodiment are not formed. Therefore, the permanent magnet is moved
in the magnet insertion hole during the drive.
The demagnetizing factor represents a ratio of amounts of the
magnetic flux on the rotor surface before and after the
energization. When the permanent magnet is demagnetized, the
performance of the motor is varied. Thus, in order to ensure the
reliability of the motor, for example, an overcurrent interruption
protective function is secured in a circuit so as to prevent a flow
of a current leading to a demagnetizing factor of 3% or more. In a
motor that is demagnetized with a small current, a breaking current
is small, and hence the motor cannot be operated in a high-load
region. Under such a background, in FIG. 5, comparing values of
currents leading to the demagnetizing factor of 3% between the
illustration example and the first embodiment, the value is larger
in the first embodiment by approximately 35%. Accordingly, it is
understood that the resistance to demagnetization is significantly
improved in the first embodiment as compared to the configuration
of the illustration example. Therefore, it is understood that the
motor of the first embodiment can be constructed as a highly
reliable motor that is not demagnetized even in the high-load
region.
Further, in the first embodiment, the air gap between the rotor
outer peripheral surface and the stator inner peripheral surface is
secured so as to be increased as approaching from the magnetic pole
center portion to the inter-pole portion. Accordingly, the magnetic
resistance of the rotor surface is increased as approaching from
the magnetic pole center portion to the inter-pole portion. Thus, a
magnetic flux density distribution on the rotor surface corresponds
to a distribution similar to a sine wave having the highest
magnetic flux density at the magnetic pole center portion.
Accordingly, a harmonic component of the magnetic flux density can
be reduced to reduce vibration and noise of the motor. Moreover, a
part of the rotor outer peripheral surface, which is positioned on
the radially outer side with respect to the side surface portion of
the permanent magnet that is easily demagnetized, is formed by the
second arc. Thus, the air gap between the tooth portion and the
above-mentioned part is wide so that the magnetic resistance is
increased. Thus, the configuration in which the armature magnetic
flux hardly interlinks with the permanent magnet is attained,
thereby enabling the permanent magnet to be hardly
demagnetized.
Second Embodiment
Next, an interior permanent magnet motor according to a second
embodiment of the present invention is described. FIG. 7 is a view
according to the second embodiment of the present invention in the
same manner as that of FIG. 2. FIG. 8 is a graph for showing a
relationship between a thickness of the permanent magnet and an
amount of a magnetic flux that interlinks with the stator. Note
that, the second embodiment has the same configuration as that of
the above-mentioned first embodiment except for portions described
below.
In the second embodiment, assuming that a thickness of the
permanent magnet 19 between the first arc surface and the second
arc surface (dimension in a radial direction of the arc) is
represented by T1, and a thickness of the permanent magnet 19 on
the magnetic pole center line ML is represented by T2, the
thicknesses T1 and T2 fall within a range of
0.85.ltoreq.(T2/T1).ltoreq.0.95.
In the second embodiment constructed as described above, the
following advantages can be obtained in addition to the advantages
in the above-mentioned first embodiment. When the straight surface
is formed at the magnetic pole center portion of the permanent
magnet, the magnet thickness of the magnetic pole center portion is
reduced correspondingly, and at the same time, the volume of the
magnet is reduced as compared to the structure without the straight
surface. Therefore, in the second embodiment, when the straight
surface is formed, reduction of the magnet amount and reduction of
the magnetic resistance of the magnet itself are offset so that a
suitable magnet thickness is realized in terms of securing the
amount of the magnetic flux. That is, in the second embodiment, as
described above, the thicknesses T1 and T2 of the permanent magnet
are set so as to fall within the range of
0.85.ltoreq.(T2/T1).ltoreq.0.95. Thus, as shown in FIG. 8, even
when the magnet thickness of the magnetic pole center portion is
reduced due to the presence of the straight surface, due to the
effect of offsetting the reduction of the magnet amount and the
reduction of the magnetic resistance of the magnet itself, the
reduction of the amount of the magnetic flux can be suppressed to
1% or less. Note that, as a specific example, the permanent magnet
19 is constructed to have the above-mentioned thickness T1 of 6 mm
and the above-mentioned thickness T2 of 5.5 mm.
Third Embodiment
Next, an interior permanent magnet motor according to a third
embodiment of the present invention is described. FIG. 9 is a view
according to the third embodiment in the same manner as that of
FIG. 3. Note that, the third embodiment has the same configuration
as that of the above-mentioned first embodiment except for portions
described below.
The straight surface of the permanent magnet according to the
present invention is not limited to be formed on the magnetic pole
center line ML, and at least one straight surface only needs to be
formed on the radially-inner magnet contour surface of the
permanent magnet. In the third embodiment, a permanent magnet 219
has two straight surfaces 249 on a radially-inner magnet contour
surface 243, and this pair of straight surfaces 249 are arranged to
be line symmetric with respect to the magnetic pole center line ML
as the center. Note that, although not illustrated, a magnet
insertion hole configured to receive the permanent magnet 219 also
has a pair of straight surfaces configured to be held in contact
with the pair of straight surfaces 249 of the permanent magnet 219.
That is, also in the third embodiment, similarly to the case of the
above-mentioned first embodiment, the magnet insertion hole and the
permanent magnet 219 are configured to be closely held in contact
with each other except for the presence of the air gap portions at
side end portions.
Also in the third embodiment described above, advantages similar to
the above-mentioned first embodiment are obtained. That is, the
movement of the permanent magnet can be restricted without relying
on the presence of the abutment portions of the magnet insertion
hole to be held in contact with the side end surfaces of the
permanent magnet.
Fourth Embodiment
Next, an interior permanent magnet motor according to a fourth
embodiment of the present invention is described. Note that, the
fourth embodiment has the same configuration as that of any one of
the above-mentioned first to third embodiments except for portions
described below.
The interior permanent magnet motor according to the fourth
embodiment has a feature in a relationship between the straight
surfaces of the magnet insertion hole and the permanent magnet and
an air hole. As a specific illustrated example, FIG. 1, FIG. 2,
FIG. 4, and FIG. 7 described above are given. As illustrated in
FIG. 1, FIG. 2, FIG. 4, and FIG. 7, on a radially inner side of the
rotor core with respect to the magnet insertion holes, in
particular, on a radially inner side of the rotor core with respect
to the straight surfaces, there is formed at least one air hole
(plurality of air holes 71 in the illustrated example) configured
to allow a refrigerant and an oil to pass therethrough when the
interior permanent magnet motor is mounted on a compressor. Note
that, reference symbol 73 denotes a rivet hole. The air holes 71
and the rivet holes 73 are alternately arrayed in the
circumferential direction, and the air holes 71 and the rivet holes
73 are arrayed equiangularly. Each of the air holes 71 and the
rivet holes 73 are positioned in a corresponding inter-pole
portion.
In the illustrated example, three air holes 71 are arc-shaped
elongated holes that are convex toward the radially-inner magnet
contour surfaces 43 (243) of the permanent magnets 19 (219). The
three air holes 71 are arranged on the same circumference about the
rotor center so as to be separated equiangularly. Each of the
elongated holes is arranged across radially inner parts of
corresponding two permanent magnets to attain a configuration in
which the air hole 71 is positioned on the radially inner side (on
the magnetic pole center line) with respect to the straight surface
49 (249) of each of all the permanent magnets. It is preferred that
an interval between the straight surface and the air hole be
reduced so as to easily cool the permanent magnets, and it is
preferred that the interval between the straight surface and the
air hole on the magnetic pole center axis be 3 mm or less. In this
case, as an example, the interval between the straight surface and
the air hole on the magnetic pole center axis is set to 2 mm.
Also in the fourth embodiment described above, advantages similar
to the advantages of any one of the corresponding first to third
embodiments are obtained, and further, the following advantages are
obtained. That is, the straight surface is formed on each of the
magnet insertion holes to enlarge a space on the rotor core on the
radially inner side with respect to the magnet insertion holes, and
the air holes are formed in the enlarged space. Therefore, when the
interior permanent magnet motor is used in the compressor, the
refrigerant and the oil easily pass through the air holes, thereby
being capable of enhancing the performance of the compressor.
Further, the thickness of the permanent magnet is smallest at the
magnetic pole center portion, and accordingly, the magnetic flux
density in the vicinity of the magnetic pole center portion may be
slightly lowered. However, the air holes are formed on the radially
inner side with respect to the straight surfaces, thereby attaining
an effect of cooling the magnetic pole center portion of each of
the permanent magnets. Thus, a residual magnetic flux density of
each of the magnets is increased due to the cooling, thereby being
capable of suppressing the lowering of the magnetic flux density,
which may be caused when the magnet thickness is reduced at the
magnetic pole center portion.
Further, in general, when the air holes are formed in the vicinity
of the radially inner side of the permanent magnets in a wide
range, the air holes function as the magnetic resistance, and the
amount of the magnetic flux generated from each of the permanent
magnets is reduced. However, in the rotor in which the arc-shaped
permanent magnets are each arranged so that the convex portion side
faces the center side of the rotor, the interval between the
permanent magnet and the air hole can be increased as approaching
from the magnetic pole center portion to the inter-pole portion.
Thus, the effect of the magnetic resistance by the air holes can be
alleviated, thereby being capable of attaining structure that less
influences the performance in the magnetic path.
Fifth Embodiment
Next, as a fifth embodiment of the present invention, there is
described a rotary compressor having the interior permanent magnet
motor according to any one of the above-mentioned first to fourth
embodiments mounted therein. Note that, the present invention
encompasses a compressor having the interior permanent magnet motor
according to any one of the above-mentioned first to fourth
embodiments mounted therein. However, the type of the compressor is
not limited to the rotary compressor.
FIG. 10 is a vertical sectional view of the rotary compressor
having the interior permanent magnet motor mounted therein. A
rotary compressor 100 includes the interior permanent magnet motor
1 (motor element) and a compression element 103 in an airtight
container 101. Although not illustrated, a refrigerating machine
oil for lubricating each of sliding portions of the compression
element 103 is stored in a bottom portion of the airtight container
101.
The compression element 103 includes, as main components thereof, a
cylinder 105 arranged in a vertically stacked state, a rotary shaft
107 serving as a shaft rotated by the interior permanent magnet
motor 1, a piston 109 to be fitted by insertion into the rotary
shaft 107, a vane (not shown) dividing an inside of the cylinder
105 into an intake side and a compression side, an upper frame 111
and a lower frame 113 being a pair of upper and lower frames into
which the rotary shaft 107 is to be rotatably fitted by insertion
and which are configured to close axial end surfaces of the
cylinder 105, and mufflers 115 mounted on the upper frame 111 and
the lower frame 113, respectively.
The stator 3 of the interior permanent magnet motor 1 is directly
fixed to the airtight container 101 by a method such as shrink
fitting or welding and is held thereby. The coil of the stator 3 is
supplied with power from a glass terminal fixed to the airtight
container 101.
The rotor 5 is arranged through intermediation of an air gap on the
radially inner side of the stator 3, and is held in a rotatable
state by the bearing portions (upper frame 111 and lower frame 113)
of the compression element 103 via the rotary shaft 107 (shaft 13)
in the center portion of the rotor 5.
Next, an operation of the rotary compressor 100 is described. A
refrigerant gas supplied from an accumulator 117 is taken into the
cylinder 105 through an intake pipe 119 fixed to the airtight
container 101. The interior permanent magnet motor 1 is rotated by
energization of an inverter so that the piston 109 fitted to the
rotary shaft 107 is rotated in the cylinder 105. With this, the
refrigerant is compressed in the cylinder 105. The refrigerant,
which has passed through the muffler 115, rises in the airtight
container 101. At this time, the refrigerating machine oil is mixed
into the compressed refrigerant. When the mixture of the
refrigerant and the refrigerating machine oil passes through the
air holes formed in the rotor core 11, the refrigerant and the
refrigerating machine oil are promoted to be separated from each
other, and hence the refrigerating machine oil can be prevented
from flowing into a discharge pipe 121. In this manner, the
compressed refrigerant is supplied on a high-pressure side of the
refrigeration cycle through the discharge pipe 121 arranged on the
airtight container 101.
Note that, as the refrigerant for the rotary compressor 100, R410A,
R407C, R22, or the like that has hitherto been used may be used,
but any refrigerant such as a refrigerant having a low global
warming potential (GWP) can also be applied. In view of the
prevention of global warming, a low GWP refrigerant is desirable.
As typical examples of the low GWP refrigerant, the following
refrigerants are given.
(1) A halogenated hydrocarbon having a carbon double bond in the
composition; for example, HFO-1234yf (CF3CF.dbd.CH2) is given. An
HFO is an abbreviation of a Hydro-Fluoro-Olefin, and an Olefin is
an unsaturated hydrocarbon having one double bond. Note that, a GWP
of HFO-1234yf is 4.
(2) A hydrocarbon having a carbon double bond in the composition;
for example, R1270 (propylene) is given. Note that, R1270 has a GWP
of 3, which is smaller than that of HFO-1234yf, but has higher
combustibility than HFO-1234yf.
(3) A mixture containing at least any one of a halogenated
hydrocarbon having a carbon double bond in the composition or a
hydrocarbon having a carbon double bond in the composition; for
example, a mixture of HFO-1234yf and R32 is given. HFO-1234yf,
which is a low pressure refrigerant, is large in pressure loss and
is thus liable to degrade the performance of the refrigeration
cycle (in particular, in an evaporator). Therefore, a mixture of
HFO-1234yf and R32 or R41 that is a refrigerant higher in pressure
than HFO-1234yf is positively used in practical.
Also in the rotary compressor according to the fifth embodiment,
which is constructed as described above, advantages similar to the
advantages of any one of the corresponding first to fourth
embodiments described above are obtained.
Sixth Embodiment
Further, the present invention may be carried out as a
refrigeration and air conditioning apparatus including the
compressor according to the above-mentioned fifth embodiment as a
component of a refrigeration cycle. Note that, configurations of
components other than the compressor of the refrigeration cycle of
the refrigeration and air conditioning apparatus are not
particularly limited.
In the above, the details of the present invention are specifically
described referring to the preferred embodiments. However, it is
apparent to those skilled in the art that various modifications may
be made based on the basic technical concept and the teachings of
the present invention.
* * * * *